Dive into the source code here. Similar to Godot it features some neat platform support: Linux, Android, WebGL, Windows, iOS and OSX (resorted for significance ;) ); but unlike it you have much more and more common scripting languages at your disposal: JavaScript, TypeScript, C++, and C# scripting in the works. Especially the latter could be interesting if someone manages to make an Unity3D compatibility layer for migrating and open-sourcing Unity games...

For a nice overview, don't miss the GamesFromScratch video and introduction tutorial (from back in December 2015 when it was not yet MIT licensed):